Automatic fire protection apparatus



1963 J. c. HAGGOTT ETAL 3,113,624

AUTOMATIC FIRE PROTECTION APPARATUS 2 Sheets-Sheet 1 Filed June 21, 1962 e 9 r mr w r f N m a 6 r W; r mflx 4 k C WW my Y B Dec. 10, 1963 J. c. HAGGOTT ETAL 3,113,524

AUTOMATIC FIRE PROTECTION APPARATUS 2 Sheets-Sheet 2 Filed June 21, 1962 FIG. 6

INVENTO J'O MI C'. #1466 r l/AATEE J74. Call MOE L; w

United States Patent M 3,113,624 AUTOMATIQ FIRE PROTECTION APPARATUS John C. Haggott, Marion Road, Westport, Conn, and Walter J. A. Connor, 67 Hillcrest Ave, Summit, NJ. Filed June 21, 1962, Ser. No. 204,198 5 Claims. c1. 169-5) This invention relates to an automatic fire protection apparatus, and, more particularly, it relates to an automatic fire protection apparatus in which a fire extinguishing fluid is released in the vicinity of a fire to extinguish the fire, the releasing of the extinguishing fluid being confined to the area or locality of the fire.

In conventional automatic fire protection devices, such as the well-known sprinkler systems, a quenching fluid, usually liquid, is released at a predetermined location relative to the sprinkler head or heads, whenever a fire occurs. Should a fire occur spaced appreciably from a sprinkler head, the quenching fluid will be released after enough time elapses to effect opening of the head by the spread of the fire to the zone of the sprinkler head. This frequently causes considerable unnecessary damage to property, such as water damage when water is used as the fire extinguishing liquid, especially when the fire is small or localized and starts at a point relatively remote from the nearest sprinkler head. Moreover, such systems are expensive, and the well-known sprinkler systems are unsightly for use in homes. Such systems do not lend themselves to providing protection of areas near or within the walls, doors, windows, etc., to extinguish fires starting near such areas before such fires make headway and reach the interior of the room.

It is an object of the present invention to provide an automatic fire protection apparatus in which the fire quenching fluid, desirably water, but which can be any available fire extinguishing fluid, gaseous or liquid, is ap plied chiefly to the zone of the fire, thereby avoiding unnecessary damage to other areas, which apparatus is sensitive and responsive to the start of a fire throughout its effective length to apply the fire extinguishing fluid to chiefly the locality of the fire.

Another object of this invention is to provide such fire protection apparatus, which, if used, can readily be placed in condition for re-use.

Still another object of this invention is to provide such automatic apparatus for fire protection, involving tubular members in which the fire extinguishing fluid is maintained for release upon the occurrence of a fire in the locality of a tubular member, which tubular member ruptures at a point in the area of the fire to release the fire extinguishing liquid, with the rupture confined to the locality or area of the fire.

A further object of this invention is to provide an automatic fire protection apparatus which forms an integral part of architectural and/ or ornamental members, such as mouldings, chair rails, cornices, frames, including picture frames. stair riser mouldings, stairway hand rails, and the like. Thus the fire protection apparatus of this invention blends with the architecture of the room, building or other structures, and combines in one and the same structure fire protection utilitarian and ornamental functions.

Still another object of this invention is to provide an automatic fire extinguishing apparatus which can be utilized for conveying hot or cold water for plumbing service, heating or air conditioning, can readily be installed to protect any desired area at low cost, and after release of the fire extinguishing fluid to put out a fire, can readily be conditioned for re-use.

In accordance with this invention, the automatic fire protection system comprises a polypropylene duct or interconnected series of polypropylene ducts having therein a static or flowing body of fire-extinguishing fluid,

3,113,624 Patented Dec. 10, 1963 preferably water, the polypropylene duct or ducts being constructed to have a relatively thin wall thereof extending substantially the full length thereof, exposed to the atmosphere, wherever fire protection is desired. Thus, for example, the polypropylene duct can be formed as an integral part of a wall moulding extending completely about a room or along one or more walls thereof, base or wall boards, hand rails, window frames, door frames, cornices and other structural and ornamental members employed in building construction so as to provide the relatively thin wall portion thereof, properly spaced relative to the member carrying same to be exposed to the atmosphere when said member is in place. Alternatively, a structural or supporting member can be used, shaped to receive the polypropylene duct, desirably in the form of tubing, to provide structural support for the duct and expose to the atmosphere a longitudinally extending thin wall area thereof which, as hereinafter more fully explained, provides the automatic fire protection.

In the interest of brevity of expression, in this specification, the expression duct will be used hereinafter to mean the polypropylene duct which forms the essential part of the fire protection apparatus of this invention.

The thickness of the thin walled portion of this duct is such that upon exposure to fire the thin wall melts readily and provides an opening through which the fire extinguishing fiuid flows. The thickness of this thin wall portion exposed to the atmosphere can vary somewhat, depending upon the grade of polypropylene used and/ or the static pressure or" the fluid in the duct. Employing presently available commercial grades, having a softening point of from 300 to 350 F., preferably about 335 F., a thickness of the order of inch, is satisfactory. The invention, however, is not confined to these dimensions.

An important feature of this invention is that polypropylene is the material of construction of the ducts. Polypropylene is unique among the known plastic and other construction materials, rendering it eminently satisfactory as the material of construction of the automatic fire protection apparatus embodying this invention. The thin wall sections of polypropylene rupture quickly when exposed to fire in the localized area of the fire and, surprisingly, when the fire extinguishing fluid flows through the opening or openings thus formed, the walls defining the opening or openings appear to be cooled, and this phenomena evidently is responsible for the opening or openings being localized, i.e., confined to the area of the fire and not spreading along the length of the duct. Poly propylene is light, has a specific gravity of about 0.9, which makes the ducts easy to handle and install. Polypropylene is fungi and corrosion resistant and can be obtained in many desired shapes and colors. It has a melting point of about 300 F. and higher and hence can be used safely in homes, factories and other buildings without danger of rupture under climatic conditions encountered except when exposed to fire temperatures, when the thin wall area melts quickly to provide the opening or openings through which the extinguishing fluid flows.

The above noted and other objects and advantages of the invention will be apparent from the following de tailed description of the invention, taken in connection with the accompanying drawings showing, for purposes of exemplification, a number of preferred embodiments, without, however, limiting the claimed invention to these illustrative instances. In the accompanying drawings,

FIGURE 1 is a schematic vertical section and part elevation of a dewelling embodying the automatic fire protection apparatus of the present invention;

FIGURES 2 to 8, inclusive, show several embodiments of the novel component, namely, the duct, positioned in difierent architectural and/ or ornamental members;

FIGURE 2 is a cross-sectional view of an embodiment in which the duct is carried by a separate support or mounting member;

FIGURE 3 is a fragmentary view, in the nature of a perspective view, partly in section and showing a wall of a building having the duct formed in a cornice member .above a window on the inside of the wall, and also showing a duct on the outer side of the same wall;

FIGURE 4 is a fragmentary perspective, partly in section, showing a duct in which the supporting member for the duct and the thin wall section thereof are integral and positioned along the wall board at the base of a wall;

FIGURE 5 is a fragmentary perspective view, partly in section, showing a duct and a mounting member therefor mounted along the sides of a wall;

FIGURE 6 is a perspective view, partly in section, of a duct and different form of mounting member therefor, particularly designed for use on ceilings and similar surfaces;

7 FIGURE 7 is a perspective view, partly in section, similar to FIGURE 6 but showing a different form of mounting member for the duct; and

FIGURE 8 is a perspective view, partly in section, showing a pair of ducts and a mounting member therefor, particularly designed for use as a hand rail, for example, for a stairway.

Referring to FIGURE 1 of the drawings, there is shown for purposes of exemplification a substantially complete automatic fire protection apparatus installed in a typical dwelling. The present invention, it will be understood, can be used in all structures, including factory buildings, whether of a permanent or temporary type, dwellings having one or more rooms or enclosures, garages, etc. For illustrative purposes, the dwelling shown in FIGURE 1 involves a tank 10, which can be a storage tank disposed in the attic, supplying liquid, such as water, to the downwardly extending pipes 11 and 12. Tank 10 can be a tank forming part of a hot water circulating system supplied with hot water from a suitable source, such as a hot water heater in the basement. Alternatively, it can be a storage tank from which water is supplied to the faucets and other outlets in the dwelling, tank 10 communicating with a suitable water supply equipped with a conventional control to maintain a constant level of liquid therein.

Pipe 11 communicates with the horizontal duct 13 extending the full length of wall 14 directly above the window 15 in this wall. It also communicates with the horizontally extending duct 16, which has a U-shaped portion 16 positioned adjacent window 15, and the horizontally extending duct 17 beneath the floor 18, providing protection for the ground floor room 19. Duct 17 is connected with duct 21 just below the ceiling 22 of the garage 23 adjacent the dwelling.

Pipe 12 communicates with a duct 24 positioned immediately beneath the ceiling 25 of room 26. It also communicates with a duct 27 at chair rail level, which duct 27 is connected through a U-shaped duct 28 with duct 29, in turn connected through a U-shaped duct 31 with duct 32. The U-shaped ducts 28 and 31 are positioned adjacent the window frames or, as pointed out hereinafter, can be part of the window frame. Pipe 12 also communicates with a horizontally extending duct 33 posiitoned just beneath the ceiling of the basement space 34.

A conduit 35 leads from a main 36, interconnecting the two pipes 11 and 12, and communicates with a duct 37 built into the stair rail, as hereinafter more fully described. A duct 38 positioned beneath the stairway communicates at its upper end through a connection 41 with the horizontal pipe 42 which interconnects the vertically extending pipes 11 and 12.

Tank 10 also communicates through the riser 43 which extends through the roof 44 with an exterior duct 45, suitably mounted above the roof. In this way, all of the ducts are maintained full of fire extinguishing fluid from the storage tank 10. Any suitable fire extinguishing fluid, liquid or gaseous, which has the property of extinguishing a fire, can be used, including conventional foam-type liquids which blanket the fire, preventing access of oxygen to the zone of combustion. Heavy gases, acting in the same manner, can also be used. The preferred fire extinguishing fluid is water, because it is cheap and readily available. The fire extinguishing fluid within each duct can be static or flowing, as discussed more fully hereinafter.

In the automatic fire extinguishing apparatus shown in FIGURE 1 the tank 10 maintains the ducts communicating therewith full of fire extinguishing fluid; for this purpose tank lil is provided with a pump (not shown) for supplying those ducts, e.g., 45, positioned at a higher level than tank 10 and maintaining the entire system under adequate pressure to insure flow through any openings formed in the ducts. In a system in which all of the ducts are disposed below the level of the tank It), and the head of fluid in this tank supplies the necessary pressure to effect flow when rupture takes place in any of the ducts, a pump need not be used except to fill the tank It Alternatively, the ducts may be part of the circulating system through which, say, heating or cooling water is circulated continuously. For example, it may be part of the conventional water supply system employing the ducts instead of the usual pipes for supplying water to the sinks and other appurtenances of a dwelling. The ducts may take the place of the usual pipes in a dwelling through which, say, water is supplied for flushing or other purposes. Thus, the automatic fire protection apparatus of this invention not only provides fire protection but also serves other utilitarian purposes, such as forming part of the conduit system required in a dwelling or factory for the supplying of water and other fluids. The important factor is that the ducts contain at all times either a static or flowing body of fluid, desirably liquid, which when released has satisfactory fire extinguishing properties.

As indicated, the duct and the support or mounting therefor can have different forms of construction, depending upon the particular location of the duct with reference to the portion of the dwelling or other enclosure in which it is used. Thus, for example, the construction shown in FIGURE 2 is designed for particular use on a roof or other exterior area. In this modification, a supporting member 51, desirably of metal or rigid plastic, has a leg or base portion 52 provided with an integral semi-spherical mounting member 53. The leg portion 52 has a threaded member 54 arranged to be threaded into the supporting surface 55 which, for example, can be the roof of a building, and thus fix member 51 in place on the desired surface. It will be appreciated that FIGURE 2 is a section through the member and that it runs in a longitudinal direction for the full length of the area which it is desired to protect. Thus, in the case of a roof, member 51 is of a length equal to the length of the roof. Polypropylene duct 55 is disposed within member 53, making a tight fit. As shown in FIGURE 2, the area 57 of the polypropylene tube 56 constitutes the thin wall area which is exposed to the atmosphere and which, upon occurrence of a fire, ruptures to permit fiow therethrough of the extinguishing fluid therein. The remainder of the periphery of tube 56 is protected by the relatively thick walls of the supporting member 53. The form of duct shown in FIGURE 2 can, of course, be made with a supporting member 53 extending the full length of the duct and provided at spaced points along its length with the downwardly extending legs or fastening members corresponding to 52.

In FIGURE 3, 61 indicates a longitudinally extending cornice member moulded or extruded from polypropylene of the shape shown in section in this figure, so as to have a concave area 62 extending the length of the cornice contiguous to a convex area 63. As shown in FIGURE 3, the moulding is formed with a central tubular duct 65 in portion 64 running its full length and having the peripheral or thin wall area 66 substantially tangent to the concave area 62; the thin wall area 66 of the duct 65 is exposed to the atmosphere. This construction provides a moulding or similar member of integral construction which can be placed along the walls at any desired height, e.g., as shown in FIGURE 3 above the window. The duct 65 is, of course, connected to a source of fire extinguishing liquid or can have a static body of such liquid therein after the moulding is positioned and the ends of the moulding suitably sealed by end closures to maintain the liquid therein.

A suitable ornamental cornice member 67, which, for example, can form the gutters of a dwelling, is made of metal, such as aluminum or other desirable corrosionresistant metal, being extruded in the shape shown in FIG- URE 3. This member 67 is formed with a longitudinally extending passageway 68, dimensioned to receive the polypropylene tube, which is forced into the opening 68 to make a close fit therewith. When the polypropylene tube 69 is in position, the wall 70 thereof is positioned contiguous to the concave portion of the cornice 67, along the open area of this concave portion, thus exposing a longitudinally extending thin wall portion of the tube to the atmosphere.

The embodiment of FIGURE 4 is particularly designed for use as the bead mould for stairwell stringers or on the mop boards of dwellings, etc. In FIGURE 4, 71 is an interior wall near the base of which the mop board 72 is positioned. The duct in this embodiment is constituted of all polypropyllene extruded to shape and comprises a relatively thick ornamental member 73 having a thin wall portion 74 running longitudinally the full length thereof and positioned so that it is exposed to the atmosphere. Contiguous to this thin wall portion 74 is a relatively thick flange 75 which merges into the cylindrical wall 76 defining the tubular opening 77. Cylindrical wall 76 in turn merges into a thickened corner area 78, having a flat surface 79 providing a supporting surface for the duct, which supporting surface rests on the mop board 72.

FIGURE 5 shows a duct construction in which the mounting member 81 of metal or rigid plastic is shaped, as shown in this figure, so that it comprises a semi-cylindrical supporting surface 82 and mounting legs 83, 84 extending the full length of each unit of the construction. Bolts or screws 85 are positioned where the legs join, at spaced intervals along the length of the mounting member. These screws or bolts are designed to fasten the mounting member 81 to a wall or other surface. The polypropylene duct 85 is fixed to the mounting member 81 in the semi-cylindrical holding portion thereof. For example, it can be adhesively bonded or otherwise suitably secured to this mounting member. When so mounted, the lower area 86 constitutes the thin wall exposed to the atmosphere.

The structure of FIGURE 5 is particularly designed for positioning or mounting the ducts near the upper portions of walls and other supporting surfaces so that the base portion of the polypropylene tube is exposed to the atmosphere. It will be noted that the relative arrangement of the thin wall portion of the polypropylene tube in the structure of FIGURE 5 is the reverse of that in FIGURE 4, which latter figure shows a mounting construction for the mop board, i.e., near the base of a room, whereas FIGURE 5 shows a construction designed for use near the upper portion of a room, along the side walls thereof.

FIGURE 6 shows a mounting structure particularly designed for use on ceilings or similar surfaces. In this construction 91 is the mounting member, desirably extruded from metal, such as aluminum, or suitable plastics. This member is shaped to provided the lateral wings 92 and 93 adapted to contact the underside of ceiling 94 and the intermediate semi-cylindrical connecting portion 95 dimensioned to snugly receive the polypropylene tube 96, so that approximately half or less of the periphery of this tube for its full length is exposed to the atmosphere, as clearly shown in FIGURE 6. Supporting member 91 is provided with bolts, screws, or other hanging members 97 at spaced intervals along its length for securing the member to the ceiling or other surface. The construction of FIGURE 6 is designed especially for use on ceilings where it is desired to position a single duct along the median of the ceiling.

FIGURE 7 shows a different construction for mounting the duct on ceilings. This construction is particularly designed as an inexpensive unit for garage areas or for use on roofs. It comprises a supporting member 101, which can be extruded in the shape shown, i.e., as a truncated cylinder, truncated along the longitudinal axis of the cylinder to provide a wall extending in cross-section from about 180 to 220 or more, leaving a longitudinally ex tending opening 102 between the ends 103 and 104 of the truncated cylinder. Member 101 can be extruded to shape from aluminum or other metal or, if desired, suitable plastic materials which are fire-resistant. At spaced points along the length of the wall of the mounting member 101, mounting screws or bolts 105 are provided, the heads of which are set in countersunk openings 106. The polypropylene tube 107 is suitably fastened, as by bonding, to the support 101, thus automatically producing the thin wall area 108 thereof, which is exposed to the atmosphere when the assembly is mounted as shown in FIGURE 7.

The construction of FIGURE 7 can also be used as a roof unit. When mounted on a roof or similar surface, the thin wall area 108 of the polypropylene tube will be exposed to the atmosphere in substantially the reverse relation of that shown in FIGURE 7, i.e., above the supporting member 101, rather than below the supporting member as in FIGURE 7.

A stair rail or banister construction 110 is shown in FIGURE 8. The banister 111 can be extruded of metal, such as aluminum, shaped to provide at the opposite sides thereof, running its full length, cylindrical supporting or retaining members 112 and 113. A rectangular groove or opening 114, running the full length of the banister 111, is formed therein and is arranged to receive the upstanding supporting members or rungs 115 of the stairway. Polypropylene tubes 116 and 117 are suitably mounted in the supporting surface 112 and 113, respectively, as, for example, by being bonded thereto with a suitable cement. When so mounted, the major periphery of each of the tubes 116 and 117 are adequately protected by the banister 111 and the downwardly extending areas 118 and 119 constituting the thin wall portions of the ducts which, when exposed to fire conditions, rupture in the locality of the fire to permit the flow of the fire extinguishing liquid in the ducts therethrough to extinguish the fire.

It will be understood that in all modifications, the ducts communicate with a source of fire extinguishing fluid such, for example, as the storage tank 10, and either have therein a static body of such fluid or a flowing body. When, however, a fire occurs in the locality of a portion of the duct, the thin wall area of the duct in that locality melts and ruptures, permitting the fire extinguishing liquid to be discharged through such rupture. As the liquid flows therethrough, it exercises a cooling influence on the ruptured walls defining the opening and, surprisingly, the rupture does not travel or extend along the length of the thin-walled area, but remains localized.

When the fire has been extinguished, the ruptured portion can readily be repaired by applying a patch of polypropylene sufliciently large to cover the opening, and fusing or adhesively bonding the patch to the walls of the tube. Polypropylene, being thermoplastic, can readily be repaired by applying heat to the areas surrounding the opening, and fusing a fresh piece of polypropylene thereto. Alternatively, a new section of tube can be introduced where required. In the modification of FIGURES 2, 5, 6, 7 and 8, involving a separate mounting member for the polypropylene tube, a fresh section of tube can be used to replace the damaged section and thereafter suitably connecting the ends of the required section to the source of fire extinguishing liquid, or providing it with the necessary body of such liquid in those cases where a static body of fire extinguishing liquid is maintained in the tube.

The dimensions of the polypropylene tube can be varied, depending upon the size of the installation and the area to be protected. In general, a polypropylene tube having a diameter of about A of an inch to an inch will be found satisfactory, both from an aesthetic and practical standpoint. Polypropylene tubing of larger or smaller diameter can, however, be used, but the size of the tubing should be adequate to provide discharge of fire extinguishing liquid at a reasonably rapid rate to accomplish the extinction of the fire.

It will be noted that the present invention provides an automatic fire protection apparatus which is easy to install, which, when a fire breaks out, will release the fire extinguishing liquid chiefly in the locality of the fire and therefore will not cause unnecessary damage in other localities. The polypropylene ducts can readily be restored to condition for re-use by patching or replacing the ruptured portion. The polypropylene ducts are comparatively inexpensive to install, and can be installed as part of an architectural structure, such, for example, as part of a banister, chair rail, cornice, etc.

Since different embodiments of the automatic fire protection apparatus of this invention could be made without departing from the scope of this invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A fire protection apparatus comprising a supporting member adapted to be mounted on a ceiling and having a longitudinally extending semi-cylindrical supporting member provided with laterally extending wings on the opposite sides thereof, and a polypropylene tube fixed to said semi-cylindrical supporting member, the said supporting member enveloping the major portion of the periphery of said polypropylene tube for the full length thereof and thus reinforcing the said major portion of the periphery for the full length thereof, leaving exposed to the atmosphere the base portion of said tube, said base portion being of a thinness to melt and rupture readily when subjected to fire conditions, said tube being maintained full of fire extinguishing liquid.

2. An automatic fire protection apparatus comprising a longitudinally extending polypropylene duct containing fire extinguisher fluid therein for the full length thereof, said duct extending for substantially the full length of locality for which it is desired to provide fire protection, said duct through substantially its full length having (1) a minor portion of its periphery in a direction transverse to its axis exposed to the atmosphere and consisting of a thin polypropylene wall capable of maintaining the fire extinguisher fluid therein confined within the duct but readily and quickly ruptured when exposed to fire, and (2) the remainder major portion of the periphery in a direction transverse to its axis consisting of a thicker Wall which maintains said duct substantially intact for substantially its full length to provide a passageway for flow of fire extinguisher fluid therethrough, notwithstanding the rupture of a portion of said thin wall due to fire, the flow of fire extinguisher fluid through said rupture effecting cooling of the polypropylene walls defining the ruptured portion and thus preventing spreading of the rupture along the length of said duct thereby confining the opening formed by said rupture to the locality of the fire.

3. An automatic fire protection apparatus comprising a longitudinally extending polypropylene duct containing fire extinguisher fluid therein, said duct extending for substantially the full length of the locality for which it is desired to provide fire protection, said duct through substantially its full length having a minor portion of its periphery in a direction transverse to its axis exposed to the atmosphere and consisting of a thin polypropylene wall capable of maintaining the fire extinguisher fluid therein confined within the duct but readily and quickly ruptured when exposed to fire, the remaining major portion of the periphery of said duct being confined within and supported by a supporting member which snugly engages the said remaining major portion of the periphery to reinforce and protect the polypropylene walls of said duct thus providing a passageway for flow of fire extinguisher fiuid through said duct to a ruptured portion of said thin wall upon formation of a rupture therein due to fire, the fiow of fire extinguisher fiuid through said rupture elfccting cooling of the polypropylene walls defining the ruptured portion and thus preventing spreading of the rupture along the length of said duct thereby confining the opening formed by said rupture to the 10- cality of the fire.

4. The automatic fire protection apparatus of claim 3 in which the said supporting member is a separate sup porting member having a portion arranged to be mounted on a suitable surface and a duct supporting surface shaped to conform with the shape of the duct, the said duct supporting surface reinforcing and protecting the walls of said duct except for the said thin minor wall portion.

5. An automatic fire protection apparatus in the form of a Wall cornice of polypropylene having a concave portion running the length thereof and a duct in said concave portion extending the full length thereof, having a portion of the wall defining said duct tangential to said concave portion and providing a peripheral thin wall area of said duct extending in a longitudinal direction along the periphery of said duct for substantially the full length thereof, which thin wall area is exposed to the atmosphere, the remainder of the periphery of said duct being disposed within said wall cornice and being strengthened and reinforced by the polypropylene material of said wall cornice, said duct containing a fire extinguishing fluid.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A FIRE PROTECTION APPARATUS COMPRISING A SUPPORTING MEMBER ADAPTED TO BE MOUNTED ON A CEILING AND HAVING A LONGITUDINALLY EXTENDING SEMI-CYLINDRICAL SUPPORTING MEMBER PROVIDED WITH LATERALLY EXTENDING WINGS ON THE OPPOSITE SIDES THEREOF, AND A POLYPROPYLENE TUBE FIXED TO SAID SEMI-CYLINDRICAL SUPPORTING MEMBER, THE SAID SUPPORTING MEMBER ENVELOPING THE MAJOR PORTION OF THE PERIPHERY OF SAID POLYPROPYLENE TUBE FOR THE FULL LENGTH THEREOF AND THUS REINFORCING THE SAID MAJOR PORTION OF THE PERIPHERY FOR THE FULL LENGTH THEREOF, LEAVING EXPOSED TO THE ATMOSPHERE THE BASE PORTION OF SAID TUBE, SAID BASE PORTION BEING OF A THINNESS TO MELT AND RUPTURE READILY WHEN SUBJECTED TO FIRE CONDITIONS, SAID TUBE BEING MAINTAINED FULL OF FIRE EXTINGUISHING LIQUID. 